Polymers have been modified with various additives in attempts to reduce the flammability (or increase the combustion resistance). Such additives have included phosphites, phosphates, thiophosphoric acid esters containing halogenated alkyl radicals and other halogenated organic compounds. With many such additives, they must be added at relatively high weight percentages that may adversely affect the physical and/or optical properties of the resulting articles. Polytetrafluoroethylene has been added, as an anti-drip and flame retardant agent, to many polymers, but adversely affects the clarity and transparency of molded articles made therefrom. Glass fibers may be added, but the addition adversely affects the polymer matrix and optical properties. In many applications, polymer compositions are rendered opaque by the addition of pigments to mask the reduced optical properties.
More recently there is an increasing need for new flame-retardants for polymer applications. Although existing products are effective at providing flame retardancy at low cost, concerns have been raised regarding the health and environmental risks as they are consider environmentally persistent, bioaccumulative materials. In some European countries there are proposals to ban the use of halogenated and heavy metal containing retardants.
Azido containing compounds and polymers (“azido polymers”) are important in the fields of explosives and propellants because the azido (—N3) group is highly energetic and can be incorporated into a polymer or oligomer at high weight percentage loadings. A useful class of azido polymers are oligomers, polymers or copolymers described as azido-substituted polyethers, e.g., glycidyl azide polymer (“GAP”) and bis(azidomethyl)oxetane polymer (“BAMO”). Generally, the product of polymerization is a relatively low molecular weight polymer or oligomer (e.g., 500-25,000 number average molecular weight). Alternatively, it can be a higher molecular weight polymer (e.g., 25,000-100,000 MW) as described in U.S. Pat. Nos. 3,694,383; 3,645,917; 4,483,978; and 4,879,419.